MagSonic: Magnesium production at the speed of sound

Our award-winning MagSonic technology uses carbothermal reduction and a supersonic nozzle to directly produce high quality magnesium metal. It is an efficient and cost-effective alternative for producing magnesium, using up to 70 per cent less carbon dioxide-equivalent emissions than traditional methods.

The Challenge

Stopping magnesium oxidation

A lot of the current commercial production methods for magnesium rely on silicothermic and electrolytic processes, where the mineral ore is extracted.

MagSonic produces magnesium rapidly and in a way that's better for the environment.

Magnesium is a very reactive metal so one of the biggest challenges with these processes is the tendency for magnesium to revert to magnesium oxide as the reaction products cool.

Our Response

Cooling greater than the speed of sound

We created a new process for magnesium production, which relies on carbothermal reduction and a supersonic nozzle, to rapidly cool the magnesium vapour, preventing the reversion reaction.

Our researchers engineered a system that allows ultra-rapid quenching (cooling) of magnesium vapour as it is produced. At high-temperature, magnesium vapour and carbon monoxide gas, produced via carbothermal reduction, is passed through a Laval nozzle at four times the speed of sound. The nozzle is essentially a rocket engine, cooling the gases in milliseconds. The magnesium rapidly condenses and solidifies, and can then be separated from the carbon monoxide, resulting in magnesium metal.

Magnesium powder may be recovered from the process directly, or high-purity metal ingot can be produced after distillation.

[Music plays and title appears: MagSonic Magnesium production at the speed of sound]

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It could also reduce greenhouse gas emissions from production by 50 – 85 per cent depending on the electricity source.

[Title appears: What happens in the MagSonic process?

[Image changes to show an animated stack of pressed magnesium briquettes]

Pressed briquettes of magnesium oxide and carbon are reacted under an inert atmosphere. As briquettes are loaded in they are heated to above 170,000 degree Celsius. At these temperatures magnesium oxide reacts with the carbon to produce magnesium vapour and carbon monoxide gas. The chemistry is also called carbothermal reduction.

[Gases can been seen rising from the pile of briquettes]

The hot gases containing metallic magnesium at a temperature above its boiling point are drawn to the supersonic nozzle.

[A thick cloud of gas has risen to the top of the briquettes and magnesium cells appear]

Here the gases are cooled extremely quickly to prevent the reoxidation of the magnesium. The process cools the gases in around 55-milliseconds.

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The magnesium condenses, much like the steam from a kettle forming droplets of metal. At this point the droplets, still moving faster than the speed of sound, continue to cool, travelling through a series of sonic shocks as they slow down.

[Image changes to show animated powder particles travelling to a chamber]

They soon freeze into metal powder particles. The powder particles travel into a large chamber which keeps them time to completely cool and solidify. From this chamber the mixture of powder and cooled gas is drawn towards a cyclone.

[Image changes to show the particles being swirled and the gas and particles being separated as they travel down the spiral]

Here a swirling motion separates the powder, which travels downward in a spiral, while the gases are removed. The cool, solid magnesium powder is collected at the bottom of this cyclone. Magnesium powder is very reactive and must be kept away from any oxygen sources. Magnesium is then purified and cast into slabs.

[Computer generated image appears of a sphere made up of tiny particles which are moving around quickly]

Cleaner and cheaper availability of this lightweight metal will have flow on effects such as lighter more fuel efficient vehicles. CSIRO continues to work with partners to accelerate the technology and bring it to market.

The Results

Supersonic award winner

Our team has demonstrated production of both powder and purified magnesium in the laboratory and is now focused on improving product quality and yield, to be scaled up to pilot plant construction and operation.

Cleaner and cheaper availability of this lightweight metal will have flow on effects such as lighter more fuel efficient vehicles.

The MagSonic technology received the 2011 Institution of Chemical Engineers (IChemE) innovation and excellence award for Sustainable Technology.

We continue to work with partners to accelerate the technology and bring it to market.

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